Device for reducing the idling losses in hydrodynamic brakes

Abstract

In a hydrodynamic brake (1), in order to reduce the ventilation losses, adjustable baffles (2, 20) are situated between a rotor (3) and a stator (4). During idling, when oil has been evacuated from the brake (1), one or more baffles (2, 20) of angular cross section in the outer area of the toroidal chambers (31, 41) separate the chambers via a radially inward projecting annular leg (21), a leg cylindrically situated in an axial direction abutting against the inner wall (52) of a chamber (5). During operation of the brake, that is, when the hydrodynamic brake (1) is filled with oil, the radially inward projecting leg (21) is located with its front edge (29) behind the toroidal chambers (31, 41). When only one baffle (20) covering the entire periphery of the outer area of the toroidal chambers (31, 41) is installed, slits (23, 28) are disposed in the radially inward projecting annular leg (21) to obtain the adequate elasticity. The actuation in the radially outward and inward end positions is obtained via an actuation device (6, 60), a specially advantageous design being a piston-cylinder unit (60) having two pistons (61) and a driver device on the pistons and drivers on the baffle (20), the inner position being obtained via springs (62) and the outer position via the pressure of a pressurized fluid in a pressure chamber (63) located between both pistons (61).

We claim: 
     
       1. A hydrodynamic brake (1) including a movable baffle system (2, 20, 21, 22, 25, 27), for reducing ventilation losses between rotor and stator toroidal chambers (31, 41) of said hydrodynamic brake (1) during idle operation of said brake when oil has been evacuated from said brake (1), said baffle system including at least one annular shaped baffle (2, 20) movable between an extended position proximate an inner periphery of a common chamber between said rotor and said stator toroidal chambers (31, 41), in said extended position, said annular shaped baffle (2, 20) radially reducing said common toroidal chamber between said rotor and stator toroidal chambers (31, 41) thereby reducing ventilation losses between said rotor and stator toroidal chambers (31, 41), and during braking operation wherein said hydrodynamic brake (1) is filled with oil, said at least one annular shaped baffle movable to a retracted position proximate an outer periphery of said rotor and stator toroidal chambers (31, 41), said movable baffle system characterized in that said at least one annular baffle (2, 20) is of angular cross-section and includes an annular leg (21) coupled perpendicular to an axially extending cylindrical leg (22) of said at least one annular baffle (2, 20), said annular leg (21) projecting inwardly into said common toroidal chamber between said rotor and stator toroidal chambers (31, 41) and said perpendicular axially extending cylindrical leg (22) abutting radially inwardly from a wall (51, 52) when said at least one annular baffle (2, 20) is disposed in said extended position during said idle operation, an wherein said annular leg (21) is disposed proximate said outer periphery of said rotor and stator toroidal chambers (31, 41) and wherein said cylindrical leg (22) abuts radially outwardly against said wall (51, 52), said annular leg (21) and said cylindrical leg (22) disposed radially outside said rotor and stator toroidal chambers (31, 41) when said at least one annular baffle (2, 20) is disposed in said retracted position during said braking operation; and wherein said movable baffle system includes at least one actuation device, for selectively effectuating movement of said at least one annular baffle (2, 20) between said extended position during idle operation and said retracted position during braking operation.   
     
     
       2. A hydrodynamic brake according to claim 1, characterized in that said annular shaped baffle (2) includes one annular shaped baffle disposed about the entire inner periphery of said common toroidal chamber region between said toroidal chambers, said one annular shaped baffle including first and second ends, for allowing differences in diameter of said one annular shaped baffle when said one annular shaped baffle moves between said extended and retracted positions and wherein said one annular shaped baffle (2, 20) includes elasticity between the extended and retracted positions of said baffle (20) and the differences of diameter associated with said extended and retracted positions provided by a plurality of slits (23, 28) distributed over an inwardly facing periphery of said inwardly facing periphery of said inwardly projecting annular leg (21) of said baffle (20). 
     
     
       3. A hydrodynamic brake according to claim 2, characterized in that said plurality of slits (23, 28), in said inward projecting annular leg (21) of said baffle (20) are designed so as to be generally entirely closed in the extended position of said baffle so that said inwardly projecting annular leg (21) situated between said rotor and stator toroidal chambers (31, 41) has no opening proximate said first and second ends of said annular baffle. 
     
     
       4. A hydrodynamic brake according to claim 3, wherein said actuation device includes a piston-cylinder unit (60). 
     
     
       5. A hydrodynamic brake according to claim 4, characterized in that a housing (65, 11) of said piston-cylinder unit (60) is connected with the housing (11) of said hydrodynamic brake (1). 
     
     
       6. A hydrodynamic brake according to claim 5, characterized in that said piston-cylinder unit (60) includes two pistons (61) biased toward a central region of said piston cylinder housing (65) by means of spring tension applied by first and second springs (62);   wherein an annular shaped pressure chamber (63) is disposed between said two pistons (61);   each of said two pistons (61) having a driver device (64); and   wherein first and second drivers (25) proximate said first and second ends of said annular shaped baffle and forming said one space region (24) are provided, and wherein said first and second drivers (25) engage with said driver device (64) of each piston (61) of said cylinder-piston unit (60).   
     
     
       7. A hydrodynamic brake according to claim 6, characterized in that said first and second drivers (25) are formed by a bent leg (27) in said cylindrical leg (22) of said annular baffle (20); and   wherein said bent leg (27) is stabilized in a defined position via a reinforcement (26).   
     
     
       8. A hydrodynamic brake according to claim characterized in that said piston-cylinder unit (60) has a foot-like housing (11) in which is provided a bore (65);   said bore (65) is outwardly closed via two locking screws (66);   wherein in an inner area of said bore are disposed said two pistons (61) forming an annular pressure chamber (63) between said two pistons (61) in said central region of said bore;   said driver device (64) in each respective piston (61) including an annular recess (64);   wherein between said two locking screws (66) and each of said two pistons (61), each provided with a long protrusion (68), a respective one of said first and second compression springs (62) is situated, which biases both pistons (61) into the central region of said bore proximate each other when said annular chamber (63) is not filled with pressurized fluid; and   in said housing (11) between a respective chamber (5) and said bore (65) of said piston-cylinder unit (60), a respective aperture (12) is provided for each driver (25) of said one annular shaped baffle (20) and said apertures (12) are closed by said pistons (61) both when said two pistons (61) are biased into the central region by said first and second springs (62) and when said two pistons (61) are urged in an outer position by an actuation pressure in said pressure chamber (63).   
     
     
       9. A hydrodynamic brake according to claim 8, characterized in that when said pistons (61) are urged into said central region via said springs (62), via the driver device (64) and via the first and second drivers (25) on said baffle (20), each of said first and second drivers (25) abuts along with said cylindrical leg (22) on an inwardly situated wall (52) of said respective chamber (5) and in said position, the radially inward projecting annular leg (21) of said baffle (20) separates said toroidal chambers (31, 41) and in the manner of a partition, reduces in diameter said common toroidal chamber (31, 41). 
     
     
       10. A hydrodynamic brake according to claim 8, characterized in that in the outer position of said two pistons (61) attained via the pressure in said pressure chamber (63), via said driver device (64) of said pistons and via said first and second drivers (25) of said baffle (20), each of said first and second drivers (25) abuts along with said cylindrical leg (22) on an outwardly situated wall (51) of said respective chamber (5) and in said position the radially inwardly projecting annular leg (21) of said baffle (20) is located behind said common toroidal chambers (31, 41). 
     
     
       11. A hydrodynamic brake (1) including a movable baffle system (2, 20, 21, 22, 25, 27), for reducing ventilation losses between rotor and stator toroidal chambers (31, 41) of said hydrodynamic brake (1) during idle operation of said brake when oil has been evacuated from said brake (1), said baffle system including one annular shaped baffle (2, 20) disposed about an entire inner periphery of a common toroidal movable between an extended position proximate said inner periphery of said common chamber between said rotor and said stator toroidal chambers (31, 41), in said extended position, said annular shaped baffle (2, 20) radially reducing said common toroidal chamber between said rotor and stator toroidal chambers (31, 41) thereby reducing ventilation losses between said rotor and stator toroidal chambers (31, 41), and during braking operation wherein said hydrodynamic brake (1) is filled with oil, said at least one annular shaped baffle movable to a retracted position proximate an outer periphery of said rotor and stator toroidal chambers (31, 41), said movable baffle system characterized in that said at least one annular baffle (2, 20) is of angular cross-section and includes an annular leg (21) coupled perpendicular to an axially extending cylindrical leg (22) of said at least one annular baffle (2, 20), said annular leg (21) projecting inwardly into said common toroidal chamber between said rotor and stator toroidal chambers (31, 41) and said perpendicular axially extending cylindrical leg (22) abutting radially inwardly from a wall (51, 52) when said at least one baffle (2, 20) is disposed in said extended position during said idle operation, an wherein said annular leg (21) is disposed proximate said outer periphery of said rotor and stator toroidal chambers (31, 41) and wherein said cylindrical leg (22) abuts radially outwardly against said wall (51, 52), said annular leg (21) and said cylindrical leg (22) disposed radially outside said rotor and stator toroidal chambers (31, 41) when said at least one annular baffle (2, 20) is disposed in said retracted position during said braking operation; said one annular baffle including means for providing elasticity in said one annular baffle for allowing said annular baffle to move between said extended and retracted positions, said means for providing elasticity including one space region between first and second ends of said one annular baffle, for allowing differences in diameter of said annular baffle when said one annular baffle moves between said extended and retracted positions, said means further including a plurality of slits extending radially only partially through said one annular baffle and distributed over an inwardly projecting periphery of said inwardly projecting annular leg (21) of said one annular baffle (2, 20); and   wherein said movable baffle system includes at least one actuation device, for selectively effectuating movement of said least one baffle (2, 20) between said extended position during idle operation and said retracted position during braking operation.